It was between Lostwithiel and Par. During cable renewal work, one was unfortunately severed. Not sure that it would have been sorted any faster east of Exeter as the Melksham line was disrupted for days when a signalling cable was severed a few months ago.
Indeed ... but I don't think it's so much the location as the quality of what needs fixing in the first place (modern with spares handy, or old, no spares and knackered) and the priority put on it too. "The Melksham Line" as you name it
has (my understanding) excellent permanent way for most of the route, allowing for high speed and heavy trains, but signalling / comms that is very thin an old.
Putting aside the cable issue last autumn, the line was again closed for a period on 24th January because of worries that the points at the end would get stuck with snow and ice, and that being a concern unique to this line right across the whole area. Not the first time this has happened, either. And the signalling headway must be one of the longest around; I know it's single track, but not even provision via an intermediate to have two trains following at less than quarter of an hour interval!
Looking back at Cornwall, I wonder if people work(ed) in shifts around the clock to fix the issue, or knocked off after a full day and came back refreshed the next morning to carry on ... I have seen both approaches taken depending on the importance (not the county) of the line ...